Several different methods (e.g. spectral measurements in infrared, visible and ultraviolet region, polarisation, phase and impulse characteristics measurements, colorimetry, radiation pyrometry; etc.) for the study and analysis of chemical and physical properties of biological materials are known, along with corresponding equipment.
Various approaches, that utilise methods and equipment based on the recording of fluorescence for the detection and analysis of biological materials such as DNA, are more widely known. A system and a method for detection of laser-induced fluorescence (LIF) of a biological sample is also described in US patent application US 20040012676.
Classical equipments for reading DNA chips—detectors and scanners—have two main shortcomings. First shortcoming is the low reading speed, as these apparatuses successively read the whole surface of a DNA chip. This includes areas with biological samples, as well as empty regions. Second shortcoming is that, when a point is read, its spectral characteristics are only measured in one or two points of the spectrum, which can lead to detection errors.
According to currently known approaches for the determination of the composition of a material on a carrier surface the surface is irradiated with a focused laser beam, and the resulting LIF is registered. If the surface properties have spatial difference, then the laser beam scans the carrier's surface and the intensity of the LIF is measured in each subsequent point. The total measurement time is determined by the speed of sample repositioning and the surface area to be studied.
In order to increase amount of information (or detection selectivity), a spectral filter may be placed before the element recording a fluorescence radiation, to separate certain part of the spectrum. However, to obtain adequate information about a structure of material under investigation, different filters have to be used for different wavelengths, and several consecutive scans have to be made of the object. This clearly prolongs the measurement duration in proportion with the number of wavelengths studied (i.e. filters used). The latter could be considered the primary flaw of currently known approaches and there is a need for a system that allows faster analysis without lowering the accuracy of the measurements.
Known approaches further include, for instance, U.S. Pat. No. 6,140,653, which describes an apparatus that utilises a CCD camera as an array detector for analysing a biological sample excited by white light by reading its fluorescence radiation.
The level of technology is also presented in Estonian patent application publication EE9900072 that describes an apparatus and a method for parallel detection and analysis of biopolymeric molecules marked by fluorescence markers on a two-dimensional array on a surface of thin transparent carrier. Laser beam directed into the carrier spreads within it due to the condition of total internal reflection (TIR). A certain amount of radiation (evanescent wave) exits through the surface of carrier and excites LIF of the fluorophores in the composition on biopolymeric molecules on the surface of the matrix. LIF is detected by a photosensitive element (CCD camera), providing information about fluorescent molecules bound to the matrix carrier.